XVI International Botanical Congess

As a fossil fern of the Paleozoic, Oligocarpia is generally regarded as of gleicheniaceous affinity. However, nothing is currently known about its spore ultrastructure. Recent investigation on the ultrastructure of spores in situ of O. kepingensis Wang and Wu with SEM and TEM from the Lower Permian of Xinjiang, Northwest China, indicates that the trilete spores of O. kepingensis closely resemble the dispersed genus Leiotriletes. Ultrastructurally, the exospore consists of a three-layered subdivisions, including a thin inner layer, a complex and elaborate middle layer characterized by a system of cavities, sheets and canals, and a homogeneous outer layer as well. Comparisons are made between Oligocarpia spores and those of other related fossil ferns and extant taxa based on morphological and ultrastructural evidence. These data suggest that, despite clear differences in leaf morphology, O. kepingensis has a close relationship to the family Gleicheniaceae.